1. Field of the Disclosure
The present disclosure relates to a press operation apparatus installed in an operation panel for use in various electronics for vehicles or household electric appliances.
2. Description of the Related Art
In a press operation apparatus disclosed in Japanese Unexamined Patent Application Publication No. 2005-85655, press buttons, which are formed by combining quadrilateral front knobs and square tubular retainers, are fitted into a quadrilateral opening formed in a housing. The front knobs are arranged in lines within the opening. The retainers are slidably supported by the housing. The press buttons are urged in the front side direction by springs. A substrate is installed on the back side of the housing. The substrate is provided with switches that are pressed by the respective retainers.
On the side surfaces of each square tubular retainer that face four directions, four ribs are formed so as to extend in the direction in which the retainer moves. The ribs are slidably fitted into respective guide grooves formed in the housing. An end portion of each rib and an end portion of each guide groove are tapered. When the press buttons are returned to the front side by the urging force of the springs, the tapered portions of the ribs engage with the tapered portions of the guide grooves, and the positions of the press buttons are thereby set. In this way, clearances between the quadrilateral front knobs adjacent to one another can be made uniform.
In the press operation apparatus disclosed in Japanese Unexamined Patent Application Publication No. 2005-85655, the ribs, which are formed on the side surfaces of each square tubular retainer that face the four directions, slide into the guide grooves of the housing with little clearance. When one of the press buttons slides in the housing, all of the four-directional side surfaces of the corresponding retainer are restricted by the guide grooves.
Accordingly, when one of the front knobs is pressed at a position away from the center of the front knob, the retainer attempts to lean within the housing, and this increases resistance produced when the press button is depressed with the four-directional side surfaces restricted. The front knobs disclosed in Japanese Unexamined Patent Application Publication No. 2005-85655 include rectangular front knobs. There is an extremely high probability that such a rectangular front knob is pressed at a position away from the center, and the resistance produced when the front knob is pressed to depress the retainer tends to increase. There is also a need to accurately apply the urging force of each spring at the central position of the retainer. Furthermore, there is a tendency that the press buttons cannot surely be returned to the same position as before the press buttons are pressed unless the urging force is increased.
An increase in the clearance between the sliding portions of the rib and of the guide groove may reduce a sliding load when the front knob is depressed. The increase in the clearance, however, excessively increases the unsteadiness of the press button when the press button is pressed, which results in poor operability.